Conventionally, photoacoustic imaging apparatuses that image the interiors of living organisms utilizing the photoacoustic effect are known, as disclosed in U.S. Pat. No. 6,979,292 and X. Wang et al., “A High-Speed Photoacoustic Tomography System based on a Commercial Ultrasound and a Custom Transducer Array”, Proc. of SPIE, Vol. 7564, pp. 756424-1-756424-9, 2010. Photoacoustic imaging apparatuses irradiate pulsed light such as pulsed laser beam into the living organisms. Biological tissue that absorbs the energy of the pulsed light generates acoustic waves (acoustic signals) by volume expansion thereof due to heat. The acoustic waves are detected by an ultrasound probe or the like, and the detected signals are utilized to enable visualization of the living organisms based on acoustic waves.
Meanwhile, ultrasound imaging apparatuses that employ ultrasound probes are also conventionally known, as disclosed in Japanese Unexamined Patent Publication No. 6(1994)-148154. Such ultrasound probes are equipped with ultrasonic transducers (hereinafter, abbreviated as “UT”) at the leading ends thereof. In many cases, the probes are constituted by a backing material, piezoelectric bodies, electrodes having the piezoelectric bodies sandwiched therebetween, acoustic matching layers, acoustic lenses, etc. In ultrasound imaging apparatuses, ultrasonic waves are irradiated from the UT's to subjects (human bodies), and reflected acoustic waves from the subjects are received by the UT's.
Ultrasound images are obtained by electrically processing detected signals of the reflected acoustic waves.
Note that it is also possible to obtain ultrasound tomographic images by scanning and irradiating ultrasonic waves. Known methods for obtaining ultrasound tomographic images include: the mechanical scanning method, in which UT's are mechanically rotated, swung, or slid; and the electronic scanning method, in which a plurality of UT's are provided as an array (hereinafter, referred to as “UT array”) and UT's to be driven are selectively switched by electronic switches or the like.
Such ultrasound probes are capable of detecting acoustic waves as well as ultrasonic waves. Therefore, an apparatus capable of obtaining both photoacoustic images and ultrasound images is being proposed. That is, a light irradiating section that irradiates light onto subjects is added to an ultrasound probe of this type of apparatus, and acoustic waves generated by the subjects due to irradiation of light are detected by the UT's of the ultrasound probe.